Seal assemblies are generally discussed herein for sealing a first environment or chamber from a second environment or chamber of a machinery or equipment with particular discussions extended to shaft seals in which a seal is retained within a housing on a shaft and a constant pressure is exerted by the seal on the shaft to maintain a dynamic seal between the shaft and the seal. Seal assemblies for use in static services are also discussed.
Seal assemblies for rotating, reciprocating, and face seal applications are well known in the art and are taught by, for example, U.S. Pat. Nos. 4,805,943; 4,830,344; 5,134,244; 5,265,890; 5,979,904; 5,984,316; 5,992,856; 6,050,572; 6,161,838; 6,264,205; and 6,641,141, the contents of each of which are expressly incorporated herein by reference.
Prior art polytetrafluoroethylene (PTFE) based seals are preferred by some because they provide flexibility, low-friction, and self-lubrication when used in sealing arrangements with a moving shaft, such as a rotating or reciprocating shaft. However, PTFE material used in making seals has a natural tendency to cold-flow and creep, especially in high temperature, pressure, and surface velocity applications, which are common in the oil and gas industry and other applications. Thus, operating life of PTFE-based seals is shorter than preferred when placed in these applications and conditions.
PolyEtherEtherKetone (PEEK) material, on the other hand, is better suited for high pressure, temperature and velocity applications. However, PEEK material is rigid and generally is not applicable or workable as a primary contact seal against moveable shafts, such as rotary or reciprocating shafts.
It has been found that when a relatively softer polymer seal is supported by a more temperature resistant and higher modulus polymer jacket or housing (such as PEEK or other materials as further discussed below), the sealing characteristics and operating life of the overall seal against a moveable surface is substantially improved while its propensity for distortion, cold-flow and creep is minimized.